The market requirements with respect to gas turbine dynamic behavior are becoming increasingly stringent, and the capacity to quickly and accurately adjust the gas turbine load during transient phases is required.
In order to adjust the process values of a gas turbine, closed loop controls are implemented driven on the basis of measured values, such as pressures or temperatures measured at different locations of the gas turbine or the power output measured at the generator.
FIG. 1 shows a diagram of a known closed-loop control scheme.
Known methods consist of measuring a value (for example a temperature, a pressure or a power at a particular section of a gas turbine) and comparing the measured value with a desired value to calculate an error that is supplied to a control unit that generates one or more manipulated values to be used to drive the process, such that the error becomes zero.
In order to correctly control and promptly adjust the manipulated values in accordance with the variable operating conditions, these measured values must be as accurate as possible.
When a process value (for example, the pressure at the outlet of the compressor or the temperature of the exhaust gases) is measured, the feedback value at the control unit can be affected by two delays.    1) Process delays: a machine such as a gas turbine has a thermodynamic process that involves heat transfer, mass transfer and chemical reactions. For instance, transient phases are mainly influenced by volumes and masses, since during transient phases the volumes store or discharge fuel, air, exhaust gas and the masses absorb or release heat. Volume and masses bring delays to the gas turbine process.    2) Measurement delays: sensors can introduce a pure delay (dead time) and dynamic lag in the measuring process. For example, with temperature measurements, pure delays are introduced by communications delays and measurement conditioning, and dynamic lag is introduced by the heat transfer coefficient between the source and the sensor. With other measurements, the pure delay and dynamic lag will be different (for example, pressure or power measurements are relatively fast).
Thus, the measured values received by the control unit are delayed. For example, a measured process value supplied from a sensor and received by a control unit at the time t1 is indicative of the real value in the gas turbine at a precedent time t0.
These delays slow down the gas turbine control.